1. Field of the Invention
The invention concerns a device for contact-less transmission of signals and measurement data between a rotatable part and a stationary part in a computed tomography apparatus.
2. Description of the Prior Art
A device of the above type is known, for example, from U.S. Pat. No. 5,577,026. In this known device the signal is transmitted via antennas by means of electromagnetic radiation.
A shortening of the antennas is required to increase the data rate of the transmission. The shorter the antennas, the more susceptible the transmission of the signals to external influences such as, for example, interferences or electromagnetic interference fields. A shortening of the antennas causes quality losses in the transmitted signal.
For the transmission of signals via antennas as transmission/reception devices, a certain quantity of electromagnetic radiation is radiated into the environment. Electrical apparatuses and circuits located in the proximity of the transmission/reception devices can be disrupted. The transmission/reception devices must be adapted to electromagnetic compatibility standards.
Furthermore, a very good ground contact of the transmission/reception devices is always required in the known device. Otherwise the transmission can be significantly disrupted by common mode interference voltages.
A device in which the signals are transmitted between a rotor and a stator by means of optical light is known from U.S. Pat. No. 4,525,025. The signals are injected via light conductors into a ring located on the stator, this ring being provided with a reflecting inner surface for adaptation of the transmission/reception devices. The signals are detected by reception devices mounted on the rotor. In the case of very short pulses with high pulse power, non-linear effects (for example self phase modulations) and chromatic dispersive effects occur with increasing data rates. These effects are detrimental to the quality of the transmitted signals.
DE 195 43 386 describes a device in which the transmission of the signals ensues via an optical slip ring. The light must THEREBY cover paths of different lengths in the light conductor. With increasing data rates, non-linear and chromatic dispersive effects also occur that are detrimental to the quality of the transmitted signals.
Aside from this, in the known optical light devices surface roughnesses, mechanical production tolerances and mechanical vibrations of reflective surfaces cause a mode dispersion of the light and further impair the quality of the transmitted signals. Furthermore, the signal is attenuated by multiple reflections on reflecting surfaces.